<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title></title>
    <style type="text/css">
         .box{
             width: 100px;
             height: 100px;
             border: 1px dotted blue;
             margin: 50px 50px;
         }
        .inner{
            width: 100px;
            height: 100px;
            background-color: yellow;
            transform: rotate(45deg);
            -webkit-transform: rotate(45deg);
        }
        #box div{
            transform-origin: center center;
            -webkit-transform-origin: center center;
        }
        /*
            改变一下原始点   40%  50%
                           top   center
                           100%   0%
                           bottom  left
                           bottom   right




        */





    </style>
</head>
<body>
     <div class="box">
         <div class="inner"></div>
     </div>

     <div class="box" id="box">
         <div class="inner">改变了起始点的div</div>
     </div>

</body>
</html>